Regulatory authorities and energy companies often require quantification of production and allocation of remaining reserves by producing zone for individual reservoirs and/or fields. For oil and gas wells producing from multiple zones, this is performed by reservoir monitoring through production logging and interventions into a producing well, or by incorporation of permanent instrumentation in the wellbore. More contemporary techniques to monitor production include use of tagging and/or tracer technologies (e.g., chemical, radioactive, and/or other technologies).
Performing production logs on high-rate subsea gas wells using existing techniques can be problematic. For example, the maximum rate that can be measured with a production logging tool during a well intervention may be much less than the normal well flow rates during production, rendering the acquired data questionable. Furthermore, using permanent down-hole flow measurement instrumentation can add to rig-time and complexity of a well completion, may detract from well reliability and integrity due to use of controls lines, may impede overall production rates by reducing the production inner diameter, and may present uncertainty as to the reliability of installed instrumentation at elevated levels of vibration, pressure, and temperature. As to existing tagging and tracer technology, it has a limited lifetime (e.g., one to two years) and thus cannot be expected to operate for the entire duration of the well life.